I mean...they just took it back to how Inferno Blast worked in MoP. I think they're actually out of ideas for Mages and just wanted to send us back to MoP to shut us up. They messed up with the Legion artifact abilities and Legendaries ACTUALLY making specs fun. They clearly had no replacement for when they went away and fought tooth and nail to not just baseline everything (even though from a lore and gameplay perspective, it would have made total sense to just absorb our Artifact abillities at least).
Honestly, the easiest fix would be to just reintroduce the old talent trees and iterate from there. Baseline the things players take 90-100% of the time and give us deeper customization.